SOLUTION: If 7000 is placed into an account with an annual rate of 4.5%, how long will it take to quadruple if interest is compounded annually?

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Question 378491: If 7000 is placed into an account with an annual rate of 4.5%, how long will it take to quadruple if interest is compounded annually?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Use the formula B+=+P%281%2Br%2Fn%29%5E%28nt%29. Now n = 1, r = 0.045, P = 7000. we want
28000+=+7000%281%2B0.045%29%5Et, or 4+=+1.045%5Et.
Then ln4 = t*ln1.045, or t = ln4/ln1.045 = 31.49 years.